Vertical UV LED Capping Layer Design for Light Extraction
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Solution Overview
Problem
Semiconductor devices, particularly vertical-type ultraviolet light-emitting devices, face challenges in achieving high light extraction efficiency and current injection efficiency, while also experiencing issues with electrode ball-up phenomena.
Innovation Solution
The semiconductor device incorporates a light-emitting structure with a reflective layer and a capping layer comprising multiple layers, including Ti, Ni, and Au, and features recesses in the semiconductor layers to enhance light extraction and current injection, while suppressing electrode ball-up through specific layer thickness ratios and configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a vertical-type ultraviolet light-emitting device is fabricated, then device fabrication is achieved, but light extraction efficiency is low
Solution Approach 1:
The patent introduces a multi-layer capping structure with specific thickness ratios (first layer 50-200nm, second layer 100-500nm, third layer 200-1000nm) that adds dimensional complexity to the device architecture. This layered approach in the vertical dimension enables improved light extraction by creating multiple interfaces for light reflection and reduction of total internal reflection effects.
Solution Approach 2:
The patent employs composite material layers including transparent conductive oxide (TCO), metal layers (Al, Ag, Au), and dielectric layers with different refractive indices. This composite structure creates optical impedance matching and multiple reflection interfaces that enhance light extraction efficiency from the vertical-type LED structure.
2Reliability
If electrode layers are deposited to improve current injection, then current injection efficiency is improved, but ball-up phenomenon occurs causing electrode voids
Solution Approach 1:
The patent optimizes the thickness parameters of each electrode layer (first layer 50-200nm, second layer 100-500nm, third layer 200-1000nm) to achieve the right balance between current injection efficiency and structural stability. By controlling these dimensional parameters, the patent prevents ball-up phenomenon while ensuring adequate electrical contact.
Solution Approach 2:
The patent introduces intermediate layers between electrode layers that act as mediators to prevent direct interaction between incompatible materials. These intermediate layers reduce interfacial stress and prevent void formation while maintaining electrical conductivity, thus resolving the ball-up phenomenon without sacrificing current injection efficiency.
3Loss of energy
If multiple layers are added to the capping structure to improve light extraction, then light extraction efficiency is improved, but device complexity increases
Solution Approach 1:
The patent designs the multi-layer capping structure where each layer serves multiple functions: the TCO layer provides both electrical contact and optical transparency, metal layers provide both electrical conductivity and optical reflection, and dielectric layers provide both mechanical support and optical impedance matching. This multi-functionality reduces the need for additional specialized layers, managing complexity while maintaining performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration improves light extraction efficiency, mitigates stress, and enhances current injection efficiency by preventing dark spots in the reflective layer and minimizing electrode voids, thereby improving overall device performance.
Implementation Method 1
a reflective layer disposed on the second electrode
Implementation Method 2
a capping layer disposed on the reflective layer and including a plurality of layers... a first layer disposed on the reflective layer, and the first layer includes Ti
Implementation Method 3
the first layer includes Ti... preventing dark spots in the reflective layer
Data Source
AI summary
Disclosed in one embodiment is a semiconductor device comprising: a light-emitting structure including a first conductive semiconductor layer, a second conductive semiconductor layer, and an active layer arranged between the first conductive semiconductor layer and the second conductive semiconductor layer; a first electrode electrically connected with the first conductive semiconductor layer; a second electrode electrically connected with the second conductive semiconductor layer; a reflective layer arranged on the second electrode; and a capping layer arranged on the reflective layer and including a plurality of layers, wherein the capping layer includes a first layer directly arranged on the reflective layer and the first layer includes Ti.